The geotechnical report, which was compiled by ECS Mid-Atlantic LLC., called for a shallow foundation system designed with an allowable bearing capacity of 10,000 pounds. The soils located at the site were broken down into three strata, shown to the right.

The foundation will rest on stratum II and III soils. All footings are to be at least 2.5 feet below finished grade. Isolated column footings have a minimum lateral dimension of three feet and continuous footings have a two foot minimum width. The shallow system will consist of a 4 inch thick slab on grade with 6”x6”-8/8 W.W.F. lap mesh 6 inches in all directions and concrete footings. The slab is placed over 10 mil polyethylene and 6 inches of washed gravel. The interior slabs are also to be laid over a layer of vapor barrier which is placed on top of 6 inches of washed gravel. Groundwater on the site must be at least two feet below the foundation subgrade level.

1776 Wilson utilizes a high strength concrete structural system with post tensioned two way floor slabs with drop panels. This high strength system was designed to lower the self weight of the structure and to maintain regular slab spans. The slabs range in thickness, generally ranging from 8 to 10 inches thick, and have typical 8 inch drop panels. The typical bay sizes are 30’ by 30’ with 30’ by 45’ bays in select locations. The concrete strength for the post tensioned slabs is 6000 psi.

The roof system of 1776 Wilson consists of 8 and 10 inch thick post tensioned two way slabs. The roof area is covered by vegetation from the green roof, roof pavers, or a concrete wearing slab. Below the roof surface consists of filter fabric which is accompanied by a deck drainage mat where there is vegetation. Four inches of roof insulation is used as well as hot rubberized asphalt for the waterproofing assembly. The roof areas will see added load due to the solar panels and racking system, these will add 6.6 to 8 psf to the roof dead load.

Stratum

Name

Description

I

Fill/Possible Fill

17-36 feet below site grades consisting of various amounts of sand, gravel, and clay

This table summarizes the columns found in 1776 Wilson Boulevard. Typical #3 ties are used throughout the building.

Note: While great efforts have been taken to provide accurate and complete information on the pages of CPEP, please be aware that the information contained herewith is considered a work inprogress for this thesis project. Modifications and changes related to the original building designs and construction methodologies for this senior thesis project are solely the interpretation of Joshua Urban. Changes and discrepancies in no way imply that the original design contained errors or was flawed. Differing assumptions, code references, requirements, and methodologies have been incorporated into this thesis project; therefore, investigation results may vary from the original design.

1776 Wilson's lateral force resisting system incorporates a combination of ductile reinforced concrete moment frames and reinforced concrete shear walls. The lateral loads will be distributed by relative stiffness. Starting at the roof diaphragm and then travelling through the columns that make up the reinforced concrete moment frames to the floor diaphragm. The floor slabs themselves serve as the beams in the moment frames and transfer the loads to the columns on the floor below where they eventually reach the shear walls on the bottom three stories. Once the lateral loads reach the shear walls, the walls resist lateral loads and moments about their strong axis. They can also resist transferred gravity loads from tributary members of the structure. The lateral loads will be transferred through the walls to the floor diaphragm where eventually they will be dispersed into the soil once they reach the foundation. The shear walls are 12” thick.

The lighting system proposed for 1776 Wilson has integrated controls so that everything operates as part of one system. This system communicates with fully digital relay panels, digital switches, photocells, and other various interfaces. Voltage to the equipment will be 480V (3 phase) and voltage to occupied spaces will be 208V (3 phase). Two electrical rooms, one of which will be located in the rooftop penthouse, will contain the emergency backup panels. The photovoltaic solar panel system will use a 480 volt 3 phase, 4-wire inverter to supply energy to the building.

The lighting fixtures consist of fluorescent, incandescent, and HID lighting. These fixtures are ceiling and wall mounted, recessed, and pendant lights. Occupancy sensors are to be placed throughout 1776 Wilson with low voltage sensors in select locations. Each sensor is set based on preferred environmental conditions for the particular location within the building the sensors control. Manual override via wall-mounted switches will be provided.

Mechanical

The central plant for the chilled water system of 1776 Wilson is located in the rooftop penthouse. Two water chilling units, a waterside economizer heat exchanger, and chilled water pumps accompany the main system. Each of the office floors (the 2nd floor up to and including the 5th floor) has one draw through VAV air handling unit with fan powered terminal devices installed in the ceilings. The air-handling units will have variable speed fans and MERV-13 filters.

Each floor of 1776 Wilson can be operated independently of each other. Perimeter spaces are supplied with fan powered VAV boxes with electric reheat while interior spaces are supplied with cooling only VAV boxes. Direct digital controls are to be implemented to monitor indoor environmental conditions of selected areas, to make sure preset operating conditions are maintained, and to increase the energy efficiency of the HVAC system in general.

Medium pressure loop trunk line to base building VAV boxes will be incorporated into 1776 Wilson’s shell. Discharge ducts, diffusers, and flex duct will be included. The stair towers are to have heaters.

Before construction on 1776 Wilson Boulevard began, the chosen site was redeveloped as existing structures were removed and the brownfield site was prepared for a new project. Set to contain approximately 249,000 SF of office and retail space, 1776 Wilson broke ground in February 2011. Construction began in March of 2011 and is set to finish in August of 2012. The approved site plan was purchased in 2010 by Skanska who then took over as the owner/developer for the project. The construction contract is valued at 63.5 million dollars and the delivery method is design-bid-bond. A high water table also means that extra care will have to be taken while construction occurs so that equipment doesn’t stall in the soft soils. Special care will also need to be taken due to nearby existing structures.